While at the boat with the whole network I left the Ipad and everythign running but powered down the Garmin 5212 MFD. I then started a packet capture and powered up the MFD. This analysis is based on what happens when the Garmin Network is powered up. Here is the WireShark capture in CloudShark. http://cloudshark.org/captures/824f2c3bc420 Remember the background is here: Garmin Packet Analysis Packets 37 and 38 are both ethernet layer announcements of the device becoming active. 172.16.6.0 comes on first followed by 172.16.7.0 just 0.35 seconds later. Packet 42 is the announcement of 172.16.6.0 Packets 49 and 50 appear to be the announcement of 172.16.7.0 Packet 60 is the announcement of 172.16.7.0 Lets dig into these packets. Packet 42 from 172.16.6.0 has a payload of: 92 03 00 00 98 00 ................ 00 00 01 00 00 00 02 00 5d 02 47 50 53 4d 41 50 ........].GPSMAP 20 35 32 31 32 00 00 00 00 00 00 00 00 00 00 00 5212........... 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 05 00 cc 01 00 00 ................ 42 6f 6f 74 62 6c 6f 63 6b 00 00 00 00 00 00 00 Bootblock....... 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 0e 00 ee 02 00 00 53 79 73 74 65 6d 00 00 ........System.. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 .......... Packets 49 and 50 from 172.16.7.0 has a payload of: 92 03 00 00 c0 00 ........Ph...... 00 00 01 00 00 00 03 00 8e 02 35 32 31 32 20 44 ..........5212 D 61 74 61 20 53 65 72 76 65 72 00 00 00 00 00 00 ata Server...... 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 05 00 a4 01 00 00 ................ 42 6f 6f 74 62 6c 6f 63 6b 00 00 00 00 00 00 00 Bootblock....... 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 0e 00 c6 02 00 00 53 79 73 74 65 6d 00 00 ........System.. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 03 00 fb 00 00 00 ................ 42 61 73 65 6d 61 70 00 00 00 00 00 00 00 00 00 Basemap......... 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 .. 94 03 00 00 54 00 .......d){....T. 00 00 00 00 53 6f 66 74 77 61 72 65 20 56 65 72 ....Software Ver 73 69 6f 6e 0a 37 2e 31 30 0a 43 6f 70 79 72 69 sion.7.10.Copyri 67 68 74 20 32 30 31 32 0a 47 61 72 6d 69 6e 20 ght 2012.Garmin 4c 74 64 2e 20 6f 72 20 69 74 73 20 73 75 62 73 Ltd. or its subs 69 64 69 61 72 69 65 73 00 00 00 00 00 00 00 00 idiaries........ 00 00 00 00 00 00 Packet 60 from 172.16.3.0 has a payload of: 92 03 00 00 98 00 ................ 00 00 01 00 ff ff 02 00 c3 01 47 53 44 20 32 32 ..........GSD 22 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 05 00 fa 00 00 00 ................ 42 6f 6f 74 62 6c 6f 63 6b 00 00 00 00 00 00 00 Bootblock....... 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 0e 00 40 01 00 00 53 79 73 74 65 6d 00 00 ....@...System.. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00  After the initial start-up there is some continuity of the traffic. This image has each IP Multi-Cast address plotted as its own line. Note that you can get a larger image by just clicking here. In the image notice the solid constant line which is green. (239.254.2.4) That looks like a very regular GPS position update. Once a second three packets are sent. The large purple line (239.254.2.1) seems like a sounder - It would be sending significant amounts of data as it profiles the bottom. The red and the blue are interesting in their pattern. Red is 239.254.2.2 and I believe it is an announcement - When I started the iPad without anything else it said it was available on 239.254.2.2. |